Allergic rhinitis (allergic rhinitis) (hereinafter referred to as rhinitis) and bronchial asthma (hereinafter referred to as asthma) are the most common respiratory allergic diseases in clinical practice. They are chronic airway inflammatory diseases involving mast cells, eosinophils, lymphocytes and other cells and cell components. Rhinitis has four major symptoms: itchy nose, runny nose, sneezing and nasal congestion [1]; asthma has airway hyperresponsiveness, with clinical manifestations of wheezing, coughing, chest tightness, shortness of breath and other symptoms, which can be alleviated by treatment or avoiding allergens and trigger factors [2]. Its occurrence and development have a certain regularity, usually in infants and young children with eczema or food allergy, about 3 years old, the above symptoms will automatically alleviate, but will gradually appear respiratory allergic diseases, manifested as rhinitis and asthma [3], this process is often referred to as "the natural process of allergic diseases".
In recent years, the incidence rate of allergic diseases in children has been increasing. In 2011, an epidemiological survey of rhinitis in children aged 6-13 years was conducted in Shanghai, Guangzhou, Wuhan and other capital cities. The results showed that the average prevalence of rhinitis in children was 9.8%, and the prevalence rates in Beijing and Chongqing were 14.46% and 20.42%, respectively. Since 1990, three large sample epidemiological surveys have been carried out on children under 14 years old in urban areas of China. The results show that the prevalence of asthma was 1.09% in 1990, 1.97% in 2000, and increased to 3.02% in 2010 [2,5,6], showing a rising trend. For example, Shanghai has reached 7.57%.
For respiratory allergic diseases, it is recommended to adopt a four in one combination treatment [7], namely, avoiding contact with allergens, drug treatment, allergen specific immunotherapy (AIT) and patient education. At present, drugs are mainly used in the treatment of children's respiratory allergic diseases, especially inhaled hormones, which can effectively inhibit airway inflammation, control clinical symptoms and avoid disease onset, but can not change the natural process of the disease [8].
AIT was born in 1911 and has a history of more than 100 years. In the latest international consensus of allergen immunotherapy, it has been clearly pointed out that AIT has a clear effect on rhinitis and asthma [9]. The latest domestic guidelines for the diagnosis and treatment of rhinitis also clearly proposed that AIT should be used as the first-line treatment for rhinitis, and it is recommended for clinical use [10]. Specific immunotherapy can induce immune tolerance of the body to allergens, effectively prevent the aggravation of symptoms, prevent the development of children's rhinitis into asthma, and reduce the risk of new allergen sensitization [11]. It is the only treatment method that can change the natural process of allergic diseases, and can obtain long-term curative effect [12].
Mite is the most common allergen. According to the allergen detection of 6304 patients with respiratory allergic diseases in 17 cities in different regions of China, it was found that the main allergens of rhinitis and / or asthma were dust mites, cat and dog dander, cockroach, Artemisia, etc. The positive rate of Dermatophagoides farinae was 59.0%, and children were significantly higher than adults, which was the main respiratory allergen [13]. From the perspective of regional distribution, from the north to the south, the positive rate of dust mites increased with the increase of temperature and humidity; the positive rate of dust mites in urban areas was higher than that in suburbs [14]. Mites are widely distributed in the indoor environment. It is very difficult to control the symptoms only by avoiding mite allergen exposure. Therefore, mite AIT is particularly important for children with airway allergic diseases.
Mite allergen extracts are widely used in China, but there are still many problems in the treatment process, such as the determination of indications, treatment approach, scheme, course of treatment and efficacy evaluation, etc. Therefore, in order to improve the understanding of mite AIT among clinical workers in China, we organized experts in the field of allergic diseases in children to formulate this consensus based on a large number of literature, guidelines and consensus documents at home and abroad, and integrating the experience of experts.
1 Definition and mechanism of AIT
1.1 definition of AIT
AIT is a treatment for IgE mediated allergic diseases. Children are given repeated exposure to the disease-related allergen extract, and gradually increase the dose until maintaining the dose, so as to induce the immune tolerance of children to the allergen, so that they will not produce or reduce the allergic symptoms when re exposed to the allergen. Mite AIT is the method of using mite allergen extract to achieve the above therapeutic purpose.
1.2 AIT mechanism
Allergens are ingested into the immune system through a variety of exposure pathways. Antigen presenting cells (APCs) undergo antigen presentation through class II major histocompatibility complex (MHC class II) to induce the differentiation of Th0 cells. The inflammatory factors produced by Th2 and Th17 cells in vivo can cause immune imbalance when Th0 cells differentiate into Th1 / Th2 cells, resulting in an increase in the proportion of Th2 cells. They can further secrete cytokines such as interleukin (IL) - 4 and IL-13, induce B lymphocytes to differentiate into plasma cells and produce allergen specific IgE antibodies High affinity receptor (FC ε RI) binding on the surface of inflammatory cells such as basophils enables them to recognize allergens and release cytokines [15,16,17,18].
When the body is exposed to allergens again, the specific IgE antibody on the surface of the above-mentioned inflammatory cells can recognize the allergen, degranulate the inflammatory cells, process and release inflammatory mediators such as IL, histamine, protease, leukotriene, and cause the inflammatory reaction of target organs and mucosa, and further promote the differentiation of Th0 cells into Th2 cells and the formation of specific IgE antibodies [19,20].
The allergen dose of specific immunotherapy was significantly higher than that of daily exposure. At the initial stage of increasing dose, Th0 cells could be induced to modulate
